1. Field of the Invention
The present invention relates generally to the field of television receive-only (TVRO) satellite dish antennas. More specifically, the present invention discloses a method for automatically positioning a satellite dish antenna mounted on a parked vehicle, such as a recreational vehicle, to locate geosynchronous satellites in the Clarke belt.
2. Statement of the Problem.
Over the past decade, TVRO antennas have grown substantially in popularity and are typically found in geographic areas of the United States where cable or broadcast television is not prevalent. Substantial programming exists on a number of satellites positioned in the Clarke belt, usually offering high quality programming through a paid descrambling system. Such commercially available programming from these satellites has found growing popularity among recreational vehicle (RV) users who would like to tap into this programming during their trips around the country in recreational vehicles. Initial satellite TVRO systems for recreational vehicles were simply comprised of a small TVRO dish antenna placed on the ground near the RV. The dish antenna was then manually adjusted with great care and time to locate and tune into an individual satellite. The tuning process would be repeated for tuning into another satellite. This approach was somewhat effective but resulted in considerable set-up time by the consumer and usually resulted in low quality signals in the television set.
Some satellite dish antennas are designed to mount directly on the roof of the recreational vehicle. This eliminates the need for placement and storage of the satellite dish antenna such as described above. However, the alignment of the mounted satellite dish antenna to the satellite was still difficult due to the manual adjustments involved. An example of this type of conventionally available system is manufactured by RV Satellite Systems, 2356 South Sara Street, Fresno, Calif. 93706 under the trademark "BEST MADE." This antenna is designed to be raised and lowered from inside the RV and to be easily tuned into the satellite desired. The raising, lowering, and positioning of the dish antenna is done manually using a mechanical link between the inside and outside of the RV.
A goal of TVRO satellite systems for use on RVs has been to fully automate the set-up and tuning of the dish antenna to all of the satellites. One conventionally available system providing semi-automatic set-up is manufactured by Elkhart Satellite Systems, 23663 U.S. Highway 33, Elkhart, Ind., 46517, which carries the trademark "MOTO-SAT." This system utilizes an electronic compass.
Another conventional RV satellite dish antenna providing semi-automatic positioning is manufactured by The Dometic Corporation, 609 South Poplar Street, LaGrange, Ind., 46716. This system is manufactured under the trademark "A&E TRAVEL-SAT." The satellite dish antenna is mounted on the roof of the RV. When the RV is parked at a location such as a campsite, the RV is leveled and stabilized. The operator of the system uses a compass located at least six feet in front of the coach to ascertain the present compass heading of the coach (and therefore, of the antenna). The user turns on the receiver and the TV. The TV is set to a predetermined channel. The user then keys in the present compass heading into the system controller. The user refers to a "viewer's guide" to find the azimuth and elevation readings of the city nearest the campsite where the RV is parked. These coordinates correspond to the G1 satellite and are entered into the system controller by the user. The user presses the "aim" button on the system controller and the dish commences to move. As the dish moves, the user must closely watch the TV screen and, upon seeing a quick flash of an image across the screen, press the stop button on the controller. The user then presses "left" and "right" and "up" and "down" buttons to fine-tune the satellite dish into the image. After particular satellite is found, it must be identified so that the other satellites can be found. While this system provides an improvement over the earlier manual alignment approaches, it still involves substantial user interaction and time. It also requires the user's perception to watch for the images on the TV screen. The RETRIEVER.sup.TM system made by Vicor Industries, Inc. of Mission Viejo, Calif. 92690, follows an approach similar to the above.
A wide variety of positioning systems have been used in the past for satellite dish antennas, including the following:
______________________________________ Inventor Patent No. Issue Date ______________________________________ Rodeffer et al. 5,296,862 Mar. 22, 1994 Horton et al. 5,077,560 Dec. 31, 1991 Gorton et al. 5,077,561 Dec. 31, 1991 Marshall et al. 4,907,003 March 6, 1990 Ma et al. 4,801,940 Jan. 31, 1989 Ma et al. 4,785,302 Nov. 15, 1988 Ma et al. 4,783,848 Nov. 8, 1988 Shepard 4,602,259 July 22, 1986 ______________________________________
In the parent of the present application, Rodeffer et al. disclose a method for automatically positioning a satellite dish antenna on a parked vehicle for geosynchronous satellites. The satellite dish antenna is moved to an initial search position based on a bearing provided by a magnetic compass and approximate longitude and latitude values selected by the user using the approximate geographic location of vehicle. The satellite dish antenna is then moved in a search pattern to detect a signal peak for a selected audio subcarrier frequency in a selected channel of a target geosynchronous satellite. The frequency selected is not present in corresponding channels of other satellites near the target satellite. The azimuth and elevation positions of all remaining satellites can then be calculated.
Horton et al. disclose an automatic drive for a TVRO antenna. The receiver calculates the position of each geosynchronous satellite. The antenna dish is initially pointed at each satellite and a peaking routine under operator control then maximizes signal strength for each satellite. These "peaked" positions are stored and subsequently used to repoint the antenna at each of the satellites during normal day-to-day operation.
Gorton et al. disclose a computerized antenna mount system for continuously tracking a geosynchronous satellite that has an inclined orbit with respect to the equator. The antenna mount automatically adjusts the declination angle of the ground station satellite antenna as a function of time after iteratively compiling the declination angle history from one complete orbit of a satellite.
Marshall et al. disclose a satellite receiver and acquisition system that uses an antenna search routine to maximize signal strength during setup.
U.S. Pat. No. 4,801,940 to Ma et al. discloses another example of a satellite-seeking system for a TVRO antenna.
U.S. Pat. No. 4,785,302 to Ma et al. discloses an automatic polarization control system for TVRO receivers.
U.S. Pat. No. 4,783,848 to Ma et al. discloses a TVRO receiver system for automatically locating audio signals among various audio subcarriers received from different transponders without the need for manual scanning.
Shepard discloses another example of a polar mount for a parabolic satellite-tracking antenna.